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These are two pictures of Iapetus. Some parts of the moon's surface are bright white. Other areas are very dark. The Cassini spacecraft took these pictures.
Click on image for full sizeImages courtesy of NASA/JPL/Space Science Institute.

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Iapetus

Iapetus was discovered by G. Cassini in 1672. Iapetus is the 2nd farthest moon from Saturn, with a standoff distance of 3,561,300 km. Iapetus is one of the icy moons, similar to the Galilean satellites. Iapetus is about as wide as California is long, 1440 km, or 960 miles, which makes it about the same size as Rhea, a moderately large icy moon.

Iapetus is very much like Rhea, Enceladus, Dione, and Tethys except that it looks completely different. In fact, Iapetus is unique, and does not look like any other object in the solar system in that its surface appears to be half dark and half bright.

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